This a nicely rich and satisfying meal perfect for cooler days. You can substitute broccoli or asparagus for the green beans.
In a saucepan, heat margarine until hot and bubbly. Add flour, mustard, and sage; stir quickly to combine. Stirring constantly, add milk. Cook and stir until smooth.
Add bouillon and pepper, and mix well. Reduce heat to low. Cook, stirring occasionally, until mixture is thick, 5 to 10 minutes.
Stir in the cheese, and cook until melted. Add the chicken, mushrooms, and green beans. Cook until heated through, 3 to 5 minutes.
Pour chicken mixture into a lightly greased 9x13 inch baking dish. Separate biscuits into 2 layers, making 10 circles. Arrange biscuits over chicken mixture.
Bake, uncovered, at 400 degrees F (205 degrees C) until biscuits are golden, about 10 to 12 minutes.